How to OCR a PDF (Make Scanned Documents Searchable)
OCR PDF files to make scanned documents searchable and easier to work with. When you OCR PDF documents, the software recognizes text within scanned pages so you can search, copy, and extract information more easily.
Two kinds of OCR
True image-based OCR uses a recognition engine like Tesseract to identify characters in pixel data — slow, requires significant compute, but works on pure image scans. Text-layer extraction reads an existing hidden text layer that many modern scanners and PDF tools embed alongside the visual scan — fast, accurate when present.
What PDFPuddle does
PDFPuddle uses PDF.js to extract text layers from PDFs that have them. Most modern scanned PDFs (anything from a recent multifunction printer, modern phone scanner app, or post-2018 PDF tool) include a text layer. PDFPuddle pulls that out as plain text in seconds.
When PDFPuddle returns nothing
If the result is empty or near-empty, the PDF is a pure image scan with no text layer. For those, use a dedicated OCR tool: Google Docs (free, surprisingly accurate), Tesseract (open-source, runs locally), or commercial OCR engines like ABBYY for production-grade accuracy.
OCR best practices
Higher source resolution = better OCR. Aim for 300 DPI scans. Strong contrast helps — clean white backgrounds with dark text recognize better than yellowed or speckled paper. For multi-language documents, ensure your OCR engine has the right language packs loaded.